1. Field of the Invention
The present invention relates generally to electromagnetic induction input technology, and more particularly to a sensing apparatus based on electromagnetic induction input technology and a method for controlling the same.
2. Description of the Related Art
Along with the rapid growth of markets for smart phones and other touch screen devices, extensive research has recently been conducted on these technologies. A user can input a specific command to a smart phone or other touch screen device by selecting a specific position or icon on the display of the touch screen device with a user's body part or an Electromagnetic Induction (EI) pen.
The selection through contact with a user's body part can be implemented by capacitive touch screen technology. A capacitive touch screen typically includes transparent electrodes and condensers between the transparent electrodes. As the user touches the touch screen, the touch is sensed based on the resulting changed capacity of the condensers.
However, it is difficult to provide precise input with capacitive type touch screens due to a relatively large contact area over which a user touches the touch screen a body part. In contrast, EI touch screen technology offers the benefit of operation in response to a touch over a small area with an EI pen.
The EI scheme controls generation of an electromagnetic field by applying a voltage to a loop coil disposed on a Printed Circuit Board (PCB) and controls transfer of the electromagnetic field to an EI pen. The EI pen includes a condenser and a loop and emits the received electromagnetic field in a specific frequency.
The electromagnetic field emitted from the EI pen is transferred to the loop coil of the PCB so that a position on the touch screen corresponding to the EI pen can be determined based on the electromagnetic field.
Conventionally, in order to apply an electromagnetic field to an EI pen, current flows through all loop coils arranged on a PCB for EI. As a result, power consumption in the touch screen device is increased. Especially when a portable battery is used, such as in a mobile device, increased power consumption reduces battery life, which may have significant adverse effects on user convenience.
Moreover, conventional EI technology requires a long time in order to sense input, due to each of the loop coils on the PCB being controlled to sense a change in the electromagnetic field received from the EI pen.